The European Journal of Cancer Prevention special issue on ‘Joining forces for better cancer registration in Europe’: achievements and perspectives

Cancer registration in Europe originated at the national level in the first half of the 20th century in Denmark. Since then, the process has undergone considerable expansion both in geographic terms as well as in its overall scope (from the basic initial incidence indicators to survival and clinical outcomes). Cancer registration is a key component of ‘big data’ in oncology and has become an important instrument for aetiological and epidemiological research at the population level. In October 2016 the European Network of Cancer Registries (ENCR) and the European Commission’s Joint Research Centre (JRC) organized the 2016 ENCR Scientific Meeting and General Assembly with the theme: ‘Joining forces for better cancer registration in Europe’. Approximately 170 European cancer-registry representatives joined the event, contributing with 36 oral and 50 poster presentations. To mark the importance of this event, the JRC together with the ENCR decided to request publication of a special issue of the European Journal of Cancer Prevention (EJCP) focused on cancer registration in Europe, selecting some of the contributions of the scientific conference. This special issue presents a snapshot of the wide range of cancer registries’ activities in Europe and includes examples of the descriptive and analytical studies currently being carried out with cancer-registry data. The opening article focuses on the substantial and long-term effort of Germany in integrating its regional population-based cancer registries already in place to a nationwide implementation of clinical cancer registries (Holleczek and Katalinic, 2017). Within this strategy, half of the German states are already setting up comprehensive cancer registries integrating the tasks of both clinical and population-based cancer registries. Several methodological issues still remain to be resolved, including standards on data collection, processing and utilization to reach uniform top-quality standards. The EJCP special issue also includes the first evaluation of case-ascertainment completeness in the whole of Switzerland (Lorez et al., 2017). By applying two innovative approaches, the authors report satisfactory levels of completeness across all Swiss registries. A paper from Estonia (Paapsi et al., 2017) evaluates the impact of case under-reporting in childhood cancer estimates for incidence and survival in the calendar period 2000–2011. The estimated overall completeness of 89.5% is reflected in considerable underestimation for both incidence and survival measures, mostly because of the exclusion of nonfatal childhood cancer cases. Two other papers propose ad hoc statistical methods applied to cancer registration data. One addresses the validation of incidence rates in an Italian region not fully covered by registration (Nannavecchia et al., 2017). The method uses neighbouring incidence data, adjusting for hospitalization and mortality. The second estimates the population-based cancer-specific potential years of life lost in a cohort of cancer patients from Belgium and proposes a method applicable when accurate information on the cause of death is not available (Silversmit et al., 2017). The authors report on how the cancer-specific fraction of the potential years of life lost increases with increasing cancer-specific mortality and decreasing age at diagnosis. A number of papers report on cancer incidence, survival and end-outcome trends in different European geographic areas. Solans et al. (2017) describe the changes in the incidence and survival of Hodgkin lymphoma in Girona (Spain) over three decades, considering stage of diagnosis, histological subtype and presence of B-symptoms, that is, systemic symptoms of fever, nocturnal sweats and weight loss. They find constant Hodgkin lymphoma incidence throughout the period, and lower survival for patients with older age at diagnosis, higher clinical stage and presence of B-symptoms. Antunes et al. (2017) report on cancer survival trends for the first decade of the millennium in the northern region of Portugal, focusing on the 20 cancer sites with the highest incidence. Survival improvements are not consistent for all cancer sites; although a very good prognosis is confirmed for thyroid and prostate cancers, some cancer sites still report poor survival values. Suteu et al. (2017) show increasing cancer incidence trends over 14 years for skin melanoma and squamous cell carcinoma in Cluj County, Romania. They also analyse survival, finding improvements over the period, but low values in older ages, advanced stages and rural areas. Low registration completeness for squamous cell carcinoma may affect survival results, especially in stratified analyses. Jakab et al. (2017) consider trends of incidence and survival of childhood leukaemia over 45 years in Hungary, analysing the prognostic role of socioeconomic level of the different geographic areas. They observe a 1% annual increase in leukaemia incidence, mainly because of an increase in acute lymphoblastic leukaemia; they also report significant improvements in survival and an inverse association with deprivation level of the area of residence at diagnosis, especially for longer-term survival estimates. Zadnik et al. (2017) explore the time trends and spatial variations of mesothelioma incidence in Slovenia over the last 50 years. After an increment since 1970, mesothelioma incidence levels off after 2003. This peak was reached 30 years after the maximum value of the asbestos import curve. Spatial analysis shows mesothelioma clusters around known asbestos sources in the past, whereas more recent geographic distribution is more scattered. Kaceniene et al. (2017) report on the suicide risk among cancer patients in Lithuania over the period 1993–2012. An increment of suicide risk is shown compared with the general population, being three-fold higher for patients with advanced stages, and with the highest risk in the critical period shortly after diagnosis. This study underlines the unsatisfied clinical and psychological needs of patients, and the importance of multidisciplinary preventive interventions. Two papers integrate cancer-registry data with other sources, such as screening programme data and outdoor air pollution. Bastos et al. (2017) evaluate the effectiveness of population-based breast cancer screening in cancer mortality in the central region of Portugal. They estimate a more than 30% reduction in breast cancer mortality following the introduction of an organized screening programme. The association between several outdoor air pollutants and lung-cancer mortality is analysed at regional level in Crete, Greece (Sifaki-Pistolla et al., 2017). The authors find that high levels of analysed pollutants, especially particulate matter, are associated with a higher risk of lung-cancer mortality across geographic regions. Limited data on adjustment for smoking habits, including lack of information on duration and amount of cigarettes smoked, and absence of accounting for the latency period of lung cancer limit the interpretation of these provocative findings. The collection of detailed clinical information on patient and tumour characteristics, including stage, diagnostic exams and treatments, enables cancer registries to evaluate the cancer care patterns at the population level. Guevara et al. (2017) examine the treatment patterns and trends in the last decade for women with nonmetastatic breast cancer according to recent European guidelines in Navarra, Spain. The authors find increasing adherence to European guidelines over the last decade in this Spanish region, but still an inadequate adherence for elderly women. The last two articles address the participation of cancer patients in clinical trials. Of these, a study from the Netherlands evaluates the association between trial participation of long-term Hodgkin’s lymphoma survivors with health-related quality of life (Thong et al., 2017). The authors report nonsignificant differences in quality of life associated with the participation in clinical trials. A cohort study of cancer patients in Northern Ireland including over 50 000 patients (Donnelly et al., 2017) investigates population and disease factors associated with participation in clinical trials. The authors show unsatisfactory trial participation, especially among adult and elderly patients, but a more satisfactory one among children. The establishment of a regional cancer-trial network implied increase patient participation. The linkage between clinical trials and cancer-registry databases provides an effective instrument for monitoring changes in cancer treatment and clinical trial participation at the population level. The wide scope of relevant issues covered in this EJCP supplement, spanning from coverage and methodology of cancer registration to its implications and inferences on cancer causes, management and outcome, illustrates the critical role and importance of cancer registries over seven decades since their first establishment in Europe. The synergistic partnership of the ENCR and the European Commission since 2012 has given new impetus to the work of cancer registration in Europe. It has contributed with harmonization of data quality standards (Martos et al., 2014), the JRC-ENCR quality check software (Giusti et al., 2016) and the ENCR-JRC project on ‘Incidence and Mortality in Europe’ (http://www.encr.eu/index.php/activities/encr-jrc-project, accessed 31 August 2017), in collaboration with all European cancer registries and stakeholders that participated actively.